test_two_middleware_composition() — langchain Function Reference

Source Code

libs/langchain_v1/tests/unit_tests/agents/middleware/core/test_wrap_model_call.py lines 681–718

    def test_two_middleware_composition(self) -> None:
        """Test that two middleware compose correctly (outer wraps inner)."""
        execution_order = []

        class OuterMiddleware(AgentMiddleware):
            def wrap_model_call(
                self,
                request: ModelRequest,
                handler: Callable[[ModelRequest], ModelResponse],
            ) -> ModelCallResult:
                execution_order.append("outer-before")
                response = handler(request)
                execution_order.append("outer-after")
                return response

        class InnerMiddleware(AgentMiddleware):
            def wrap_model_call(
                self,
                request: ModelRequest,
                handler: Callable[[ModelRequest], ModelResponse],
            ) -> ModelCallResult:
                execution_order.append("inner-before")
                response = handler(request)
                execution_order.append("inner-after")
                return response

        model = GenericFakeChatModel(messages=iter([AIMessage(content="Response")]))
        agent = create_agent(model=model, middleware=[OuterMiddleware(), InnerMiddleware()])

        agent.invoke({"messages": [HumanMessage("Test")]})

        # Outer wraps inner: outer-before, inner-before, model, inner-after, outer-after
        assert execution_order == [
            "outer-before",
            "inner-before",
            "inner-after",
            "outer-after",
        ]